Description

Emerson EPRO MMS3120/022-000 — Dual-Channel Shaft Vibration Transmitter

Product Overview

The MMS3120/022-000 is a dual-channel shaft vibration transmitter manufactured by EPRO, which became part of Emerson (AMS suite) after Emerson’s full acquisition of EPRO in 2009. EPRO was originally founded in Gronau, Germany in 1970 (as a Philips subsidiary), later inherited Philips’ turbine monitoring expertise, merged with AEG’s rotating machinery protection division, and developed the world-renowned MMS6000 monitoring system. The MMS3120 is a core module within the MMS3000 transmitter series — designed to convert seismic (velocity) sensor signals into standardized industrial outputs for rotating machinery protection and condition monitoring.

In simple terms: this device sits between your vibration probes and your DCS/PLC — it takes raw vibration signals from the machine shaft, processes them, and sends clean 4–20 mA signals (plus relay alarms) so operators and control systems know whether the machine is healthy or about to fail.

MMS3120/022-000 EPRO Emerson module

What It Does

The MMS3120 accepts inputs from two independent PR9268 series seismic velocity sensors (models /20, /30, /60, /70) — these are electromagnetic velocity probes that bolt directly onto the machine bearing housing. The transmitter then:

• Converts the AC voltage from each probe into a signal proportional to vibration velocity (mm/s RMS) or vibration displacement (peak-to-peak, µm)
• Provides two independent 4–20 mA outputs (one per channel) OR a single combined output representing the maximum value of both channels — configurable via dip switches and rotary switches at the factory
• Generates 5 switchable relay/optocoupler outputs for alarm functions (danger, alarm, OK per channel)
• Offers two buffered analog voltage outputs (±5.0 V) for external analysis equipment — unfiltered dynamic sensor signals
• Performs continuous self-diagnostics on both sensors and internal circuitry — if a sensor cable breaks, shorts, or goes out of range, the “OK” relay changes state and the current output drops from 4–20 mA to 0 mA (fail-safe behavior)

The device complies with VDI 2056 and API 670 standards — the two most widely referenced standards for machinery vibration monitoring in process industries.

Model Number Breakdown

Other common variants include:

• MMS3120/022-100 — with 20–4/0 mA reversing current output
• MMS3120/022-020 — with PROFIBUS DP communication
• MMS3120/022-010 — with RS485 + EPRO V2.0 protocol

Protection & Diagnostics

The MMS3120 has a comprehensive self-monitoring system:

• Sensor cable monitoring — detects open circuit, short circuit, and signal out-of-range for each channel independently
• Internal module monitoring — checks supply voltage, output circuit integrity, and processing chain health
• Fail-safe output behavior — on any detected fault, the “OK” relay de-energizes and both current outputs drop to 0 mA — this is critical for safety-critical turbine trip applications
• Channel-normal logic — the 5 switchable outputs can be set per-channel (Ch1 OK, Ch2 OK) or combined (Ch1 AND Ch2 OK, Ch1 OR Ch2 OK) — giving flexible alarm logic without external relays